428 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[December, 



is shown how it can he ileduced from one observation alone ; but as one ob- 

 servation cannot have tlie accuracy which the mean of a greater number will 

 have, it will be better to observe correctly other readings also, such as 1-00, 

 2'On, ?yOO, 4-00, Sic, and mark these points likewise, and by taking the 

 mean of the whole, the scale can he made as accurate as it is possible to 

 graduate it. The smaller divisions of the scale can be filled up by the assist- 

 ance of the rule — " that the aberration varies inversely as the reading." 



The tube of the telescope being thus graduated, and having found the best 

 adjustment for the eye-piece to view the cross lines, mark npon the slide of 

 the eye-piece this adjustment also, and let the eye-piece he always set to this 

 mark on every observation. As this adjustment is important, and though 

 mentioned before and understood to be done previously to taking the ob- 

 servations for the scale of aberrations, tlie repeating the caution here may 

 not be considered altogether uncalled for. 



The telescope being levelled, is now prepared for taking distances ; the 

 staff being held at the distance required to be measured, the object glass of 

 the telescope is brought to as near the jiroper focus or distinct vision as the 

 eye of the observer can appreciate, the divisions of the staff counted and the 

 sum or reading taken; then, having got the reading, look at the slide of the 

 telescope, and if the focal adjustment points to the same figure as the read- 

 ing is, which it generally will do, then the reading first taken is correct, and 

 only requires the addition of the fixed quantity to make it the actual distance 

 itself; or in any case a proportional measure of the distance, if the divisions 

 of the staff do not correspond exactly with the divisions of the measure for 

 distance, but if they do correspond, then the augmented reading is the dis- 

 tance itself. 



15ut if the slide shows a reading greater or less than that read off from the 

 stafl!', then the first adjustment for focus by the eye has not been sufficiently 

 precise, and the slide must be adjusted to the same figure as the reading of 

 the staff exactly, and tlien the reading observed again through the telescope 

 and taken ; and this approximating process can be repeated as often as re- 

 quired, but once will always insure sufiicient accuracy for ordinary purposes, 

 and even this once will, in many cases, not be necessary ; this corrected 

 reading, then, with the addition of the constant, will give the distance either 

 actual or proportional as the case may be. 



15y this process, after the first correction if required, a degree of precision 

 will be attained so as to leave nothing more to be desired on this head ; and 

 by reiieating the process, the smallest imaginaiy quantity of error may be 

 got rid of, and tlius the uncertainty as to which is the true focal point for 

 any distance is removed, and all cause to doubt the accuracy of this method 

 obviated. 



Take a practical example with a 20 inch telescope, by rendering the focal 

 distance precise to the -^ part of an inch; now there being 10,000 such 

 parts in 20 inches, the greatest error in distance will only amount to the 

 -j-jpijt; part of the whole distance, and in taking a great number of distances, 

 there is no reason to suppose that even these minute errors should be more 

 on one side of the absolute truth than on the other side. It follows that in 

 the aggregate of these distances, even such minute errors will vanish by mu- 

 tually comiterbalancing each other, this being the case then, even with the 

 adjustment for focus by the eye alone, and without the first approximating 

 process, a very near approach to the exact distance is obtained in the long 

 run, and by the approximating process, a degree of precision will be attained 

 far exceeding that by the common or direct process of the chain, and the 

 more especially on uneven ground. 



PROJECTED RESTORATION OF HEREFORD CATHEDRAL. 



In May last Mr. Cottingbam made a discovery in Hereford Cathedral 

 which, while it adds greatly to the interest of that venerable fabric, furnishes 

 a valuable addition to the instnictive and pleasing remains we possess of the 

 architecture of the 11th century. The discovery referred to was made on 

 taking down the modern Italian wainscot screen, of the Corinthian order, 

 erected by Bishop Biss 120 years ago, enclosing the whole of the ancient re- 

 mains of the east end of the choir. The screen, on being removed, was found 

 to have completely shut out the view of the Ladye Chapel, which must once 

 have possessed surpassing excellence. The beautiful drawing of the restora- 

 tion, just published by Mr. Cottingbam, presents to us an architectural gem 

 of the first water. It consists of a Norman arch, above which are three Go- 

 thic windows, and between the windows and the arch, a screen or belt. The 

 arch occupies nearly the whole width of the east end of the choir, and is very 

 massive ; it is decorated with foliage and zigzag mouldings. The arch is 

 supported by four columns, with rebated pilasters, the capitals being highly 

 enriched with foliage and sculpture, the latter presenting curious devices to 

 represent the security and triumphs of the Christian. The belt running above 

 the arch is composed of 24 semi-Normal columns. The three windows are 

 of the early pointed style, and have evidently been formed since the erection 

 of the building by cutting away the Norman groining to introduce the Gothic, 

 which at the time was rising in favour. The three w indows throw a flood of 

 light on the beauties of the choir. At the time of making the discovery Mr. 

 Cottingbam found in the wall, just above the belts, five apertures of the early 

 English age, completing the narrow walk all round the choir. 



On looking into the Ladye Chapel from the high altar, a l)eautiful and un. 

 equalled effect is seen to result from the presence of two columns, wluc|, 



stand in a line with the centre of the Norman arch, and support the early 

 English groining which connects the north and south transepts, the capital 

 of one being of the Norman, and that of the other of the early English age, 

 but both erected at the same time. 



This discovery is highly important, as it adds to the proofs already obtained 

 that by slow degrees the heavy semi, circular Norman arch has passed into 

 the light and pointed Gothic. The evidence of this fact is quite clear on 

 comparing the upper with the lower part of Mr. Cottingbam 's drawing, and 

 also on noticing tbe difference between the capitals of the two pillars at the 

 entrance of the Ladye Chapel. It is much to be desired that the beautiful 

 restoration designed by Mr. Cottingbam may soon be reahzed, as it will fur- 

 nish to every admirer of cathedral architecture a treasure of unparalleled 

 beauty. The necessity for the extensive repair of the whole cathedral is but 

 too obvious. The tower, which has long been in danger of falling, is even 

 now in little better than a state of jeopardy, being shored up by a series of 

 timbers 13 inches square, so as to support the whole superincumbent weight, 

 wliile the defective piers are cut out and reinstated. It is gratifying to find 

 that the people of Hereford are fully sensible of tbe value of their venerable 

 cathedial, and that they nave wisely avoided allowing party politics to inter- 

 fere with the design of effecting its thorough and tasteful reparation. The 

 antiquarian skill and taste of the dean (Dr. Merewether), combined with the 

 zealous co-operation he receives from the canons of the cathedral, and from 

 the clergy and gentry of the neighbourhood, give a most encouraging prospect 

 of success, while the professional experience of Mr. Cottingbam is a voucher 

 for the restoration of the sacred structure to its pristine beauty and magnifi- 

 cence. 



The work is one of more than local interest, it is important to the whole 

 kingdom. Our antique buildings cannot be regarded as an insignificant part 

 of our national wealth. They show that we are not of yesterday and they 

 link us to the past. There is, indeed, a share of sanctity in the feeling that 

 would prompt us to shield from the despoiling hand of time the monuments 

 of those ancestors from whom we have received our being, our social institu- 

 tions, and many of our sacred ijrivileges. 



Let the appeal for the requisite funds, therefore, not be limited to the 

 county or the diocese ; let an opportunity of sharing in the work be afforded 

 to the taste and liberality of the country at large, and it will soon be found 

 that these time-honoured structures have friends everywhere throughout the 

 country, from John o'Groat's-house to the Land's-end. 



Martyrs' Memori.'yL. — Those of our readers who live at a distance from 

 Oxford, and who take an interest in the completion of the Martyrs' Memorial, 

 will be gratified to learn that great progress has been made in the works dur- 

 ing the last three months, notwithstanding occasional impediments from the 

 unfavourable state of the weather. The cross has been raised to about two- 

 thirds of the height of the first stage or division of the shaft, which forms 

 the base of the niches for the statues ; and though much of the detail in the 

 ornamental carving is of necessity left for the present in a rough state, till 

 the upper portion of the cross is completed, yet sufficient is expressed to give 

 a very good idea of the rich eflfect which will be produced when the whole 

 is finished. At one time we were somewhat apprehensive lest the colour of 

 the stone should prove darker than we had been led to expect ; but we have 

 been assured by competent authority that this partial discolouring will readily 

 pass off as the stone becomes more exposed to tbe action of the atmosphere : 

 and this result has already taken place in the lower part of the base, which 

 was first laid down. Me believe a similar efl'ect may be observed in the new 

 Houses of Parliament, in which the same description of stone is being used ; 

 the upper courses, which have been recently laid, appear for some time dis- 

 coloured, while those in the lower part of the walls, having been longer ex- 

 posed to the air, have already nearly assumed their natural tone of colour. 

 Tbe exterior walls of the Martyrs' Aisle, as well as of the east end of the 

 centre aisle, which it was necessary to take down and rebuild, in order to 

 throw open the whole line of tbe Martyrs' Aisle in the interior of the church, 

 have been sufficiently advanced to enable the workmen to commence laying 

 the slates upon the roof. A considerable portion also of the ornamental 

 parts, the fiuials, pinnacles, and the pierced parapet, has been set up. The 

 general effect of this aisle, when completed, w ill be very striking ; and we do 

 not hesitate to say that it will be one of tbe most beautiful specimens of 

 ecclesiastical architecture in this city. The workmanship also appears to us 

 to be very well executed. The rebuilding of the east end of the centre aisle 

 has rendered it necessary to make extensive repairs to other parts of St. Mary 

 Magdalen Church. The gable of the adjoining aisle was found to be in so 

 defective a state that it was necessary to take it down without delay ; and it 

 has been rebuilt in a style corresponding in its general character with the 

 other new work, but it is not so much ornamented in detail as the other 

 gables. We understand also that the flat plaster ceiling of this aisle is to 

 be removed, in order to open to view a handsome wooden ceiling in panels, 

 which is above it. But these, as well as some other alterations to improve 

 tbe general character of the interior of the church, will be effected entirely 

 by separate subscriptions, laised specifically for this purpose, and which are 

 w'hoUy independent of the subscription to tbe Martyrs' Memorial. We regret 

 to add, that we understand the sum of 700/. is still wanting in order to meet 

 the engagements of the committee for the Martyrs' Memorial. We believe 



